Ve/nniforiii, A'pj>f'ii(b\r. 349 



the muscle bands and the muscle sheath at the caecal end. The 

 lemur's caecum is much like an enlargement of a combined 

 human type — Treves' type A and a foetal caecum (Fig. 12). 



Without going outside the primate order, evidence is forth- 

 coming of two ways in which a caecum may recede from the 

 large to the sixiall, as in man with an appendix and the baboon 

 without an appendix. In the same order the lemur's caecum is 

 that type which 'may recede and form during that involution a 

 vermiform appendix. 



Treves' B type which, according to Deaver, represents three 

 per cent, of the human caeca, shows the appendix fully formed 

 in the fundus of the caecum. It should be regarded as the 

 earliest type of appendix. From point of origin the fundus of 

 the caecum, to the ileo-caecal valve, is the range of atrophic 

 take-up brought about by the pull of the mesenteric longitudinal 

 band. Therefore one phase of caecal atrophy, in animals which 

 develop a vermiform appendix, is a line of migration of the 

 appendix from the fundus of the caecum to the lower lip of the 

 ileo-caecal valve, a migration proceeding concurrently with 

 general caecal atrophy. Before complete atrophy of the appen- 

 dicular caecum can occur, the appendix must remain anchored 

 to the ileo-caecal valve for a time which cannot, in our state of 

 knowledge, be stated. Before that point can be approached, we 

 must discover either a wombat or a man in which complete 

 atrophy of the appendicular caecum has occurred. We do not 

 think that the discovery will be made at an early date, because 

 many human caeca are still in tlie early stages of appendicular 

 evolution and the wombat (Fig. 14) is in a stationary period, 

 his food being subjected to very slight variation. We do not 

 consider loss of the appendix by disease a true atrophic process ; 

 at present to approach the question from the standpoint of 

 sepsis is not a method free from solid objection. We have 

 already said that some animals, as the baboon, will lose the 

 caecum without the appearance of a vermiform appendix, if 

 complete atrophy of the caecum be subsequently established in 

 them. Primates as an order do not lend themselves to a com- 

 plete study of caecal atrophy, because, as far as we know, com- 

 plete atrophy has not occurred in primates. We must there- 

 fore study those changes in an order In which we have unmis- 



